Send Orders for Reprints to reprints@benthamscience.ae 1156 Mini-Reviews in Medicinal Chemistry, 2014, 14, 1156-1168 An Overview of the Pharmacological Properties and Potential Applications of Natural Monoterpenes Agata Kozioł 1 , Agnieszka Stryjewska 1 , Tadeusz Librowski 2* , Kinga Sałat 3 , Magdalena Gaweł 2 , Andrzej Moniczewski 4 and Stanisław Lochyński 1,5* 1 Department of Bioorganic Chemistry, Faculty of Chemistry, Wrocław University of Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland; 2 Department of Radioligands, Medical College, Faculty of Pharmacy, Jagiellonian University, Medyczna 9, 30-688 Kraków, Poland; 3 Department of Pharmacodynamics, Medical College, Faculty of Pharmacy, Jagiellonian University, Medyczna 9, 30-688 Kraków, Poland; 4 Department of Toxicology, Medical College, Faculty of Pharmacy, Jagiellonian University, Medyczna 9, 30-688 Kraków, Poland; 5 Institute of Cosmetology, Wrocław College of Physiotherapy, Kościuszki 4, 50-038 Wrocław, Poland Abstract: Monoterpenes, the major components of essential oils, belong to the group of isoprenoids containing ten carbon atoms. Being widely distributed in the plant kingdom they are extensively used in cuisine and human health care products. Studies have shown that both natural monoterpenes and their synthetic derivatives are endowed with various pharmacological properties including antifungal, antibacterial, antioxidant, anticancer, antiarrhythmic, anti-aggregating, local anesthetic, antinociceptive, anti-inflammatory, antihistaminic and anti-spasmodic activities. Monoterpenes act also as regulators of growth, heat, transpiration, tumor inhibitors, inhibitors of oxidative phosphorylation, insect repellants, feline and canine attractants and antidiabetics. These interesting activities which might be potentially used not only in pharmaceutical, but also food and cosmetic industries are discussed below. Keywords: Acyclic, antibacterial, anticancer, antifungal, anti-inflammatory, antioxidant, antiviral, essential oils, hypotensive and vasorelaxant, local anesthetic, monocyclic and bicyclic monoterpenes, monoterpene activity, stereochemistry. INTRODUCTION Terpenes are a structurally diverse and widely distributed family of natural products containing over 25,000 well- defined compounds isolated from all biological kingdoms [1- 3]. Terpenes possess acyclic or cyclic structures, resulting from changes within the isoprenoid chain through reactions including reductions, oxidations, cyclizations, ring cleavages or rearrangements. This wealth of terpene diversity can be attributed to enzymes known as terpene synthases, which convert acyclic prenyl diphosphates and squalene into acyclic and cyclic forms [4]. The numerous terpene synthases in plants are primarily responsible for terpene diversity. Additionally, some terpene synthases produce multiple products from a single substrate [4]. The nomenclature of terpenes is based on the number of isoprene structures that they contain. Accordingly, these compounds are classified as monoterpenes, sesquiterpenes, diterpenes, triterpenes, tetraterpenes, and polyterpenes [2, 4, 5]. Monoterpenes, sesquiterpenes, and diterpenes are considered secondary metabolites because they are not essential for *Address correspondence to these authors at the Department of Radioligands, Medical College, Faculty of Pharmacy, Jagiellonian University, Medyczna 9, 30-688 Kraków, Poland; Tel: +48 12 6205 534; Fax: +48 12 6205 700; E-mail: mflibrow@cyf-kr.edu.pl; Department of Bioorganic Chemistry, Faculty of Chemistry, Wrocław University of Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland; E-mail: stanislaw.lochynski@pwr.wroc.pl viability; however, these compounds mediate important interactions between plants and their environment [2, 3]. Studies have shown that both natural monoterpenes [5-10] and their synthetic derivatives [11-15] possess various pharmacological properties, including antifungal, antibacterial, antiviral, antioxidant, anticancer, antiarrhythmic, anti- aggregating, local anesthetic, antinociceptive, anti-inflammatory, antihistaminic and antispasmodic activities. Monoterpenes also act as regulators of growth, heat, and transpiration; tumor inhibitors; inhibitors of oxidative phosphorylation; insect repellants; feline and canine attractants; and antidiabetic agents [3, 16]. These interesting properties, which may potentially be used in pharmaceuticals and the food and cosmetic industries, are discussed below. ACYCLIC MONOTERPENES Acyclic monoterpenes (Fig. 1), such as β-myrcene (1) and configurational isomers of β-ocimene (2), are found in the oils of basil (Ocimum basilicum, Labiatae), bay (Pimenta acris, Myrtaceae), and hops (strobiles of Humulus lupulus, Cannabaceae) as well as several other essential oils. β- Myrcene (1), which is an acyclic unsubstituted monoterpene, is reported to exhibit estrogenic activity. This compound also exhibits cardiotonic and diuretic properties and can be orally, parenterally or rectally administered [17]. Pure β-myrcene (1) and β-myrcene-containing essential oils are used as intermediates for the production of terpene alcohols (geraniol, nerol, and linalool), which subsequently serve as 1875-5607/14 $58.00+.00 © 2014 Bentham Science Publishers